What makes the M6535CSi/M6 unique?The M635CSi and M6 are the BMW Motorsport-developed versions of the E24 6 Series coupe and are powered by twin-cam, 24-valve inline-six-cylinder engines known as the M88 or S38, which were both derived from those used in the M1 sports car. They also feature a revised chassis and several unique cosmetic items.

What’s the difference between the M635CSi and M6?All examples of the BMW Motorsport-developed E24 6 Series coupes are officially designated as the M635CSi. However, in both North America and Japan, they were known and badged as the "M6", both to simplify the name and to bring it in line with the other M models, specifically the M3 and M5.

When was the M635CSi/M6 first introduced?The M635CSi was introduced at the 1983 Frankfurt Motor Show.

Where was the M635CSi/M6 built?Like all 6 Series, the M635CSi/M6 was built on the normal Dingolfing assembly line, with body shells shipped from the Karmann works in Osnabruck.

Production Data

How many versions of the M635CSi/M6 were developed?BMW Motorsport developed five different versions of the M635CSi/M6: Two non-catalyst models for the European market (left-hand drive and right-hand drive), plus three distinct catalyst versions for Europe, North America and Japan (all left-hand drive).

How many of each version were produced?Model 5531 (ECE/LHD without catalyst): 3,283 produced from 02/1984 through 12/1988
Model 5532 (ECE/RHD without catalyst): 524 produced from 09/1984 through 02/1989
Model 5511 (ECE/LHD with catalyst): 117 produced from 11/1986 through 12/1988
Model 5514 (NA/LHD with catalyst): 1,767 produced from 11/1986 through 09/1988
Model 5519 (JAP/LHD with catalyst): 164 produced from 11/1986 through 03/1988

Of the 1,767 M6s produced for North America, how many were built to Canadian specification?Of the 1,767 M6s produced for North America, 135 were built to Canadian specification over three model years: 1987 (60 produced), 1988 (73 produced) and 1989 (two produced). The remaining 1,632 were all built to U.S. specification.

For a description of how the U.S. and Canadian M6s differ, please see "Cosmetics" below.

What changed during the production of the M635CSi?There were few major mechanical changes during the five-year period that the M635CSi was produced, though certain items with known mechanical defects (such as the valve springs) were updated during the course of production. However, it is worth noting that the catalyst-equipped S38 engine became available as an option in some left-hand drive European markets starting in November of 1986, concurrent with its introduction in the North American-market and Japanese-market M6s.

The biggest cosmetic changes were phased in during June of 1987. At this time, the slimmer chrome-trimmed bumpers of the European-spec and Japanese-spec models, as well as the large rubber and chrome bumpers of North American-spec models, were replaced with more modern iterations featuring body-color end caps. In addition, ellipsoid headlights and foglights replaced the halogen units of earlier cars. These were part of a reshaped front airdam that was now identical on all E24s sold worldwide and shared with the regular 635CSi. On the inside, the leather shift knob was updated to the newer ergonomic design introduced a year earlier on the E32 7 Series. In the UK market, all updated M635s received the Highline complete Nappa leather interior, which was already standard on U.S.-spec M6s and had become a very rare option in left-hand drive European-spec M635s beginning in early 1987. One small but significant final change occurred in September of 1988, when the power front seat controls were moved from the center console to the base of the seat itself.

How many examples of the M635CSi were produced after the June, 1987 cosmetic update?In total, BMW produced 1,415 examples of the M635CSi after the updated bumper and front fascia design was introduced in June of 1987. The breakdown by market-specific version is as follows:
Model 5531 (ECE/LHD without catalyst): 83
Model 5532 (ECE/RHD without catalyst): 102
Model 5511 (ECE/LHD with catalyst): 80
Model 5514 (NA/LHD with catalyst): 1,034
Model 5519 (JAP/LHD with catalyst): 116

What distinguishes the Japanese-spec M6 from the other versions?The Japanese-market M6 entered production in November of 1986 (though two pre-production examples were produced in July) and continued until March of 1988. There were 164 examples produced in total, of which 116 have the later updated bumper design that was introduced in June of 1987. Both versions are largely identical to the catalyst-equipped, European-spec M635CSi and were produced exclusively in left-hand drive. Differences include only minimal alterations to the lighting, radio and a few other minor areas. (Interestingly, Japanese-market M6s are the only E24s that appear to have been equipped with the black exhaust tips found on the E28 M5.)

All Japanese-spec M6s were fitted with a high level of standard equipment that included 415mm cross-spoke alloy wheels, power sunroof, manual rear sunshade, power front seats and a fixed rear center console with integrated air conditioning. Later cars also included heated front seats and a driver-side seat memory feature. The only major factory option appears to have been Shadowline exterior trim. Though all the usual 6 Series exterior paint selections were offered on the Japanese-spec model, interior trims were restricted to either Highland cloth (in a variety of colors) or Buffalo leather in either Anthracite (early cars) or Siamgrey (later cars).

Drivetrain

What makes the M88/S38 engine unique?The M88 and S38 engines are evolutions of the 24-valve inline-six developed for the mid-engine M1 supercar. Like that engine, both the M88 and S38 share a displacement of 3,453cc (via a bore of 93.4mm and a stroke of 84mm), and both have a four-valve crossflow cylinder head (with 37mm inlet valves and 32mm exhaust valves) designed for better breathing at high rpm. However, for their application in the M635CSi/M6, the M88 and S38 have wet-sump lubrication, specific pistons and connecting rods, as well as more advanced Bosch Motronic fuel injection/engine management.

How do the M88 and S38 engines differ?The M88 is the non-catalyst version of the S38 engine. With a 10.5:1 compression ratio, 264-degree camshafts, equal-length exhaust headers and a single-row timing chain, it is identical to the one found in European-spec E28 M5 sedans. Power is rated at 286 hp (DIN) at 6,500 rpm with 251 lb/ft of torque at 4,500 rpm. The M88 can be identified by the BMW Roundel and only the words “M Power" on its valve cover.

The S38 is the “clean” version of the M88 motor, introduced to comply with North American and Japanese emissions regulations but also offered as an option for the European-market M635CSi beginning late in 1986. It utilizes a duplex (double-row) timing chain, 248-degree camshafts, a simplified exhaust manifold and features a lower 9.8:1 compression designed to work with catalytic converters. This reduced the horsepower to 256 hp (SAE) or 260 hp (DIN) at 6,500 rpm and torque to 243 lb/ft at 4,500 rpm. The S38 can be identified by the words "BMW M Power" on its valve cover.

What kind of gearbox does the M635CSi/M6 have?The M635CSi/M6 was equipped exclusively with the Getrag 280/5 five-speed manual gearbox. Gear ratios are as follows: 3.51 (1), 2.08 (2), 1.35 (3), 1.00 (4), .81 (5). A 3.73:1 final drive was fitted to all non-catalyst models, while those powered by the S38 B35 motor (including all cars built for North America and Japan) were fitted with a 3.91:1 rear end. A limited slip differential featuring a maximum locking action of 25 percent was standard on all versions of both the M635CSi and M6.

Chassis

How is the suspension of the M635CSi and M6 different from that of the standard 6 Series?Both the M635CSi and M6 utilize a MacPherson strut/semi-trailing arm suspension design that is common to all E24 6 Series. However, it has been tuned by BMW Motorsport and features a number of unique components. The suspension of the M635CSi is more dramatically altered than that of the North American M6 and includes the following changes:
-Specific front and rear springs (also fitted to E28 M5s produced before 10/86) that are stiffer (by 15 percent) and result in a reduced ride-height (by 0.4 inches)
-Increased steering caster
-Specially-tuned Bilstein shocks (also fitted to E28 M5s produced before 10/86)
-25mm front anti-roll bar (up from 19mm)
-16mm rear anti-roll bar

The North American-spec M6 shares its springs with the standard North American-spec E24 635CSi (as well as the European-spec E28 M535i) and therefore does not benefit from a reduction in ride-height. However, it does include unique shocks and a larger (compared to the standard North American 635CSi) 21mm front anti-roll bar that is shared with the early European-spec E28 M5 and North American-spec E28 535i/535is. The rear suspension is largely identical to that the North American-spec E28 M5, complete with automatic load-leveling rear shocks. Unlike the E28 M5, however, it retinas the smaller 16mm anti-roll bar from the M635CSi.

How is the steering of the M635CSi/M6 different from that of the standard 6 Series?Both the M635CSi and M6 are equipped with a recirculating ball steering system with an overall ratio of 15.7:1. Most were fitted with regular ZF engine-speed-sensitive power assist. However, European-spec M635s were offered with an optional (and quite rare) ZF Servotronic (vehicle-speed-sensitive) system beginning with 5/88 production.

What size brakes does the M635CSi/M6 have?The M635CSi/M6 has enlarged vented front rotors that measure 11.8-inches (300mm) in diameter. These utilize four-piston calipers. The solid rear rotors, measuring 11.2-inches (284mm) in diameter, are the same as those found on the 635CSi. ABS is standard.

What are the factory wheel and tire sizes for the M635CSi/M6?There were two available wheel and tire sizes for the M635CSi. In most European markets, the standard alloy wheel was the same metric-sized version shared with both the regular E24 635CSi and E28 M5. Made of forged alloy, these measure 390mm x 165mm or 15.4-in. x 6.5-in. and carry 220/55VR390 Michelin TRX tires. However, the majority of cars were equipped with larger cross-spoke alloys measuring 415mm x 195mm (16.3-in. x 7.7-in.) wrapped in 240/45VR415 Michelin TRX tires. The original version of this cross-spoke wheel used a three-piece construction. However, due to concerns about their integrity, BMW switched to a similar one-piece cross-spoke design beginning in late 1986. These later wheels were standard equipment on all North American-spec M6s, as well as those sold in Japan.

Cosmetics

What distinguishes the exterior of the M635CSi from that of a regular 6 Series?The M635CSi has few visual clues to distinguish it from the normal 6 Series. Almost all body panels are shared with other E24s, including the body-color rear spoiler with black rubber lip. The only exception is the deeper front airdam fitted only to pre-facelift models, which is ribbed on the lower portion. There are also two M badges, one on the trunklid and one on the grille, though these could be omitted upon request. In addition, the rear-view mirror housings are painted in body color instead of the chrome finish used on all other pre-facelift 6 Series. Finally, cars equipped with the optional cross-spoke alloy wheels (in either the early or later version) have body-color fender lip extensions. After the mid-1987 facelift, the front airdam was changed to the same one fitted to all 6 Series coupes, so the M635CSi could only be identified by its M badges (if not deleted) and optional 415mm cross-spoke alloys. As with all E24 coupes, Shadowline (dechromed) exterior trim became optional on the M635CSi during 1986 and continued to be offered through the end of production.

What distinguishes the exterior of the North American M6 from that of the M635CSi?Cosmetically, all North American-spec M6s have unique grille and decklid badges with the “M6” logo. They also have a rear spoiler (not fitted by the factory to other North American 6 Series models) and the later one-piece metric-sized cross-spoke alloy wheels. Cars built for the 1987 model year (before June, 1987 production) have the bulky five-mph bumpers used on all 1978-87 6 Series in North America. The 1987 M6 also has a front airdam with additional cooling slats that was shared only with 1987 635CSi and L6 models sold in North America. Cars built for the 1988 model year (6/87 and later) have ellipsoid headlights and a slimmer 2.5-mph bumper design that is visually identical to the European-spec M635CSi of the same vintage. The front airdam on these cars is also identical to the one used on all 1988-89 6 Series. All North American M6s have chrome (non-Shadowline) exterior trim.

What distinguishes an M635CSi’s interior from that of a regular 6 Series?The interior of the M635CSi is much like that of all other 6 Series models. The only truely unique item is the instrument cluster, which contains a 280 kph/170 mph speedometer and a special tachometer with the M logo instead of an economy meter. In addition, every M635CSi is fitted with the three-spoke M-Technic steering wheel (unless equipped with the optional driver's airbag) and the same sport seats available in other 6 Series models. In some markets, these could be replaced by the wider "comfort" chairs, also shared with other 6 Series models. Finally, the battery of the M635CSi is mounted in the trunk for better weight distribution.

How does the interior of the North American M6 differ from that of an M635CSi?The M6 interior differs little from that of the M635CSi. Like the European model, North American examples have the unique instrument cluster with a 280 kph/170 mph speedometer and a special tachometer with the M logo. However, they also have a generally higher level of standard equipment, including leather sport seats with power controls and driver’s side seat memory, power sunroof, cruise control, air conditioning, rear window sunshade and an eight-speaker am/fm cassette sound system. U.S.-spec cars are further enhanced by Nappa leather upholstery with either the Highline (1987 models) or Halfline (1988 models) interior trim and a rear center console/air conditioning unit. On 1988 models, a driver’s side airbag is also standard for U.S.-spec examples. Heated front seats were standard on the Canadian-specification M6 and the sole factory option on U.S models.

How exactly are U.S-specification and Canadian-specification M6s different?All North American M6s are mechanically identical. They also have the same exterior appearance (with the exception of two additional exterior color choices for Canada). It is only on the inside that the U.S. and Canadian models can be distinguished from each other. The following are all the ways that the two versions differ, aside from having metric (Canada) or non-metric (U.S.) instrumentation:

What types of upholstery were offered on the E24 M635CSi?Many different types of upholstery were offered on the E24 M635CSi, depending on the production date and intended market. All types can be categorized into four distinct categories: cloth, leather, Buffalo leather and Nappa leather.

In most markets, the M635CSI was equipped with a cloth interior as standard equipment. The earliest examples (produced through June of 1984) were fitted with a plush, velour-like cloth in one of five colors: Anthracite, Pacific Blue, Nutria, Pearl Beige or Pine Green. This material was carried over from the other 6 Series models, where it had been offered since the mid-1982 update to the entire E24 range. Starting with July 1984 production, the M635CSi received its own unique upholstery known as Highland cloth. This check-patterned material (shared only with the E28 M5) was also offered in Anthracite, Pacific Blue, Nutria, Pearl Beige or Pine Green, and all colors were available in most continental European markets, as well as the UK. However, Japanese-market editions (Model 5519) received only the Anthracite Highland cloth. The Highland cloth continued in production until the arrival of the facelifted M635CSi in June of 1987. A this point, the Highland cloth was replaced by a more restrained cloth fabric that resembled the original velour. This was available in just four colors: Anthracite, Indigo, Natur and Silver. However, it was only offered on left-hand drive cars destined for continental Europe, as well as those headed to Japan (in Anthracite cloth only, aside from a single car with Indigo cloth).

A large portion of M635CSi coupes were optioned with the regular leather upholstery, which was available at extra cost in nearly all markets throughout the entire production period of the model. (One exception was Japan, which did not receive this type of leather upholstery at any time.) Initial leather colors were Black, Nutria, Berber Beige, Pearl Beige, Pacific Blue and Cherry. Over time, Berber Beige was replaced by Lama, Pearl Beige was replaced by Natur, Pacific Blue was replaced by Indigo, Cherry was replaced by Taurus Red and then Cardinal Red, plus Silver leather was added. Though this type of leather was discontinued on right-hand drive examples upon the introduction of the updated M635CSi to the UK market in late 1987, it continued to be offered all the way until the end of left-hand drive production in 12/88 on other European-spec examples (both Model 5511 and Model 5531).

Another type of leather upholstery that was offered right from the very start of M635CSi production was Buffalo leather. This type of leather is much more grainy and rough than the normal leather, and was initially available in just two colors: Anthracite and Nutria. Every version of the M635CSi was offered wtith Buffalo leather, including the Japanese-market edition (Model 5519). Coinciding with the introduction of the updated M635CSi in June of 1987, the Anthracite Buffalo leather was replaced by Siamgrey Buffalo leather, while Nutria Buffalo leather was replaced by Havana Buffalo leather. At the same time, Buffalo leather upholstery was discontinued on UK-market models, but continued to be offered elsewhere until left-hand drive M635CSi production ceased in 12/88.

Finally, a very soft and supple type of leather known as Nappa was introduced very late into the life of the M635CSi, roughly just two years from the end of production. Offered in Lotus White, Natur, Silvergrey or (eventually) Black, this upholstery was exclusively available in the M635CSi as part of the Highline interior option that included leather on nearly every surface of the cabin (see next question for more details). Because of its extremely high cost, only about a dozen left-hand drive European-market examples were produced with this leather option. However, all 101 examples of the facelifted right-hand drive M635CSi built for the UK market between 11/87 and 2/89 received this interior as standard equipment.

What are the Highline and Halfline interiors?The "Highline" interior refers to a special Nappa leather upholstery treatment, whereby hide is used to cover essentially every visible surface of the cabin. It includes hand-stitched Nappa leather on the seats, door panels, center console, glovebox door, headliner, sun visors, door pillars, upper door trim and dashboard. This interior was standard on all U.S-specification M6s built before June of 1987, as well as all examples of the UK-specification M635CSi that were produced after June of 1987. In some other European markets, the Highline interior could be ordered as an extra-cost option, though it was extremely expensive and only about a dozen cars were so equipped.

A special variation of the Highline interior was introduced on all U.S.-specification M6s concurrently with the cosmetic update that arrived for the 1988 model year. Unofficially known as the "Halfline" interior, it included all the same Nappa leather trim of the Highline interior with the exception of the dashboard and upper door trim, which were replaced with standard plastic items from the non-Highline interior. This slightly less luxurious interior variation was a reaction from BMW of North America, which had been forced to replace a significant amount of 1987 M6 leather dashboards after the strong sun in warmer regions of the United States had warped them beyond repair.

Both the Highine and Halfline interiors were initially offered in just three colors: Lotus White, Natur and Silvergrey. in addition, late UK-specification examples of the M635CSi were available with a Black Highline interior (also fitted to the six final U.S.-spec M6s).

Were there any special editions of the M635CSi/M6?There were no official special editions of the E24 M635CSi or M6 from BMW Motorsport GmbH. However, BMW of Great Britain offered an unofficial "Motorsport Edition" of 20 right-hand drive M635CSi coupes, all of which were produced in a single (nearly) consecutive production run between October of 1988 and January of 1989. These were equipped with all the usual UK-spec equipment, plus Shadowline exterior trim (also available on non-Motorsport M635s) and tri-color M stripe lapels (similar to those found in some E28 M5s) on the front and rear seats. Three special color and trim combinations were offered: Misano Red with Black Nappa Highline leather upholstery (10 examples produced), Nogaro Silver metallic with Black Nappa Highline leather upholstery (5 examples produced) and Macao Blue metallic with Lotus White Nappa Highline leather upholstery (5 examples produced). (Note: Production of the standard RHD M635CSi then resumed for one additional month.)

It is also worth noting that the two very last examples of the North American M6 ever produced are unique in that they were the only two made for the 1989 model year. Both VIN 2561766 (Alpine White II with Black leather) and VIN 2561767 (Salmon Silver with Black leather) were equipped to Canadian specification and feature the later E34-style power seat controls mounted directly to the seat instead of on the center console.

Color and Upholstery Selections

The following chart lists all regularly available paint colors for the E24 M635CSi & M6.

PAINT NAME

PAINT CODE

MODEL AVAILABILITY

PRODUCTION PERIOD

Arctic Blue metallic

045

5531, 5532

02/1984 through 08/1986

Henna Red

052

5531

02/1984 through 09/1984

Polaris metallic

060

5531, 5532

02/1984 through 05/1986

Black

086

5511, 5514, 5519, 5531, 5532

02/1984 through 02/1989

Graphite metallic

087

5531

02/1984 through 09/1984

Cinnabar Red

138

5511, 5514, 5519, 5531, 5532

10/1984 through 02/1989

Bronzit metallic

139

5511, 5514, 5531, 5532

02/1984 through 02/1989

Alpine White

146

5511, 5514 (Canada only), 5519, 5531, 5532

02/1984 through 12/1987

Sapphire Blue metallic

149

5531

02/1984 through 09/1984

Bahama Beige metallic

170

5531, 5532

02/1984 through 10/1985

Opal Green metallic

171

5531

02/1984 through 09/1984

Carmine Red

172

5531, 5532

10/1984 through 08/1986

Lapis Blue

173

5519, 5531, 5532

02/1984 through 08/1986

Saturn Blue

176

5511, 5531, 5532

10/1984 through 08/1986

Agate Green metallic

177

5531, 5532

02/1984 through 08/1986

Baltic Blue metallic

178

5531

02/1984 through 09/1984

Acacia Green metallic

179

5531, 5532

10/1984 through 08/1986

Basalt Blue

180

5531

02/1984 through 09/1984

Diamond Black metallic

181

5511, 5519, 5531, 5532

10/1984 through 02/1989

Emerald Green metallic

182

5511, 5531, 5532

10/1984 through 05/1987

Delphin metallic

184

5511, 5519, 5531, 5532

02/1984 through 02/1989

Cosmos Blue metallic

185

5531, 5532

10/1984 through 08/1986

Plane Tree Green metallic

188

5531, 5532

10/1984 through 08/1986

Cirrus Blue metallic

189

5511, 5531, 5532

09/1986 through 02/1989

Sable Brown metallic

196

5531, 5532

10/1984 through 08/1986

Royal Blue metallic

198

5511, 5514, 5519, 5531, 5532

09/1986 through 02/1989

Burgundy Red metallic

199

5511, 5531, 5532

02/1984 through 06/1987

Salmon Silver metallic

203

5511, 5514 (Canada only), 5519, 5531, 5532

09/1986 through 02/1989

Malachite Green metallic

205

5511, 5519, 5531, 5532

09/1986 through 02/1989

Atlantis Blue

207

5511, 5519, 5531, 5532

06/1987 through 02/1989

Mink Brown metallic

212

5531, 5532

09/1986 through 06/1987

Alpine White II

218

5511, 5514 (Canada only), 5531, 5532

12/1987 through 02/1989

Luxor Beige metallic

219

5511, 5531, 5532

09/1986 through 06/1987

Wine Red

214

5511, 5531, 5532

06/1987 through 02/1989

Misano Red

236

5532 (Motorsport Edition only)

10/1988 through 01/1989

Nogaro Silver metallic

243

5532 (Motorsport Edition only)

10/1988 through 01/1989

Macao Blue metallic

250

5532 (Motorsport Edition only)

10/1988 through 01/1989

The following chart lists all regularly available upholstery colors for the E24 M635CSi & M6.